The principle behind all available fasteners such as nails and bolts is development of intense but directionally controlled forces between them and the component(s) they are designed to fasten together. This always translates into the reliance for the "fastening function" upon the resultant shear-stress between the fastener and the component. The superior "fastening" capability of threaded fasteners over smooth nails, stems from the larger thread-area subjected to frictional stresses with the component. Numerous designs of fasteners, (nails, bolts, screws, etc.) capitalize on shapes and configurations that increase the surface area and their enhanced-mechanical holding capability to the components. Yet, none of these makes optimal use of the tremendous increase in "fastening strength" offered by chemically induced cohesive forces associated with adhesives.
While the conventional fasteners mechanically accomplish their function, introduction or regions adhesives into and about the fastening region or regions will yield superior results through chemo-mechanical means.
The benefits of adhesives are well established. Presently, when adhesives are applied in nailing, bolting and screwing operations, they are applied wastefully, inaccurately, and uncontrollably. Often the fastener is dipped into the adhesive prior to its introduction into the component being fastened or in case of "bolting", the adhesive can also be "smeared" into the hole made in the component. In either form of application, the adhesive spreads unevenly about the fastener.
In other prior art systems, a body of adhesvie carried in or on the fastener at the time the fastener is installed is subject to uncontrolled discharge where it is not wanted, to premature activation and deterioration of the adhesive. Installation may be complex and require the use of uncommon tools and techniques, removal of a partially installed fastener may be difficult, choice of adhesives is restricted, the choice of fastener sizes is limited, and gaps left between piston and body parts of some designs in prior art fasteners having adhesive reservoirs may invite corrosive attack.
In practicing the invention that is disclosed in my aforementioned related application, into a blind socket which is about to receive a fastener such as a screw, one or more capsule or capsules containing adhesive is or are first placed. As the fastener is installed, it bursts the capsule or capsules, spreading the adhesive at the fastening region. The capsules can be provided in a number of sizes and shapes, in order to facilitate placing the right amount of the right adhesive at the right place.
FIGS. 1-5 and the following related description concern the invention that is disclosed in my aforementioned related application.
FIG. 1 is a longitudinal cross-sectional view of a pre-formed socket having received a selected capsule of adhesive which is about to be ruptured by installation of a fastener;
FIG. 2 is a similar view of a later stage, in which fastener installation has been completed;
FIG. 3 is a side elevation view of a typical selection of capsules of adhesive;
FIG. 4 is a sectional view at a stage intermediate that of FIGS. 1 and 2, but of a modification; and
FIG. 5 is a sectional view at a stage intermediate that of FIGS. 1 and 4, but of another modification.
In FIG. 1, a pre-formed socket 10 is shown formed in a material 12 that is to be fastened. As shown, the material 12 representatively comprises two layers, 14 and 16, with the socket opening outwards of the layer 14 of the material 12 at 18 and having a blind end 20 within the layer 16 of the material 12. The sidewall 22 of the socket 10 is in the instance shown, cylindrical, e.g. of substantially constant diameter from mouth to blind end.
The socket 10 may be formed in any convenient manner, e.g. by drilling, punching, burning, solvent attack, melting, etc. It may be formed in respective segments before the layers 14 and 16 are juxtaposed, or it may be formed in one continuous operation after the layers 14 and 16 are juxtaposed. The layers 14 and 16 may not be of the same thickness, and the material 12 may, instead be made of one, three, or more layers. The layers 14 and 16 need not be made of the same material nor need any layer be made of homogeneous material. Any layer may itself be made of a plurality of pre-united sub-layers.
The socket 10 may initially be formed as a blind socket, or it may be initially formed as a throughhole into one end of which a plug is pre-fitted, e.g. in the region 24 to cause the socket to have a blind end 20.
In FIG. 1, the fastener that is about to be installed in the socket 10 is an utterly conventional bolt 26 having a threaded shank 28 with a tip end 30 and a head 32.
Also in FIG. 1, a capsule 34 of adhesive has already been deposited in the socket 10. In this instance the capsule 34 is shown being of prolate-spheroidal shape, and of a minor diameter nearly equal to that of the sidewall of the socket. Accordingly, as the capsule 34 is simply deposited in the socket one-small-end-first, it slides down with its long axis remaining parallel to the long axis of the socket, and comes to rest at the bottom of the socket.
As the fastener 26 in being installed is jammed of threaded into the socket 10, the capsule is compressed to its bursting point, bursts between the tip end 30 of the fastener and the socket, and covers the interface 36 of the fastener 26 and material 12. How much of the interface gets covered in this operation depends on the filled volume of the capsule relative to the space available with the socket as the fastener 26 is fully inserted, upon the porosity of the material 12, and upon the initial placement of the capsule and/or the shape of the interface as the fastener is being inserted, particularly where some of the excess adhesive may escape to the surface, e.g. at 38 or into the material, e.g. at 40.
In FIG. 3, a typical selection of adhesive capsules are shown. At A is a pile of very small capsules, e.g. from micro-size or upwards to the size of conventional prills of lawn fertilizer. At B there is an individual spherical capsule. At C there is a stack of three individual oblate-spheroidal capsules. At D there is a single prolate-spheroidal capsule. At D there is a single teardrop-shaped capsule. At F there is a capsule as at D stacked upon a capsule as at B. At G there is a generally cylindrical capsule that is smaller in diameter than the capsules shown at D and E. Each of the capsules may be provided in more than one size, more shapes than those shown may be provided. Those of various sizes or containing different types of adhesive, or the same adhesive with different setting times, or strengths, and the like or containing complementary essential components of the same adhesive, may be coded in any convenient manner, such as having the capsule wall be of one or more colors keyed to a color key, or to have the capsule wall be made of transparent material and the adhesive as visible through it be of a color keyed to a color key, or to have various symbols, indicial, patterns, etc. applied to the capsule wall, as exemplified by the three central banding stripes 42 on the capsule at G.
The term adhesive is broadly used, not only to cover materials which cure, set, react, harden, dry, crystallize or freeze and act by means of chemical bonds to provide adhesion and/or cohesion that locks the fastener in place, but also such materials, as, in the course of going from a generally fluid state to a generally solid state establish a mechanical lock or interference fit.
The provision of capsules of adhesive that are separate from the fastener 26 and from the material 12 until just before the fastener is inserted in the socket 10 accounts for many of the advantages of the improved fastener of the invention, principally because the capsule or capsules to be used in any particular securement can be selected as a separate step from selection of the fastener 26 and from provision of the socket 10. In many instances it is also important to the user to be able to see and feel the capsule before placing it in the socket, i.e. to determine that it has the size, the shape and the color or markings which common sense and/or the color chart or the like indicate should be used for the particular securement, and to determine that the quantum of adhesive contained within the capsule is not stale (has not dried-out or otherwise gone bad while awaiting the moment of installation).
It has been determined, for instance, for the typical installation shown being accomplished in FIG. 4 that three capsules 34B should be used, e.g. to provide, upon bursting, a sufficient quantity of adhesive or to give the proper proportions of a multiple component adhesive such as two red-colored capsules of an epoxy resin flanking a blue-colored capsule of hardener for the epoxy resin. At the moment depicted, the tip end of the fastener which in this instance is a nail 26', has just pierced, punctured or burst the uppermost one of the capsules. Upon the next blow of the hammer (not shown) the other capsules will be burst and the fastener 26' will be driven fully home in the socket 10, spreading the adhesive in the fastening region comparable to the showing in FIG. 2.
For the nail 26', an utterly conventional nail may be used. However what is shown is a somewhat special nail, one that is provided with at least one and preferably a plurality of longitudinal grooves 44 in its shank. These accommodate some of the adhesive so that as the adhesive sets, a mechanical interlock is formed between the fastener 26' and the material 12 via the set adhesive.
Another variation is shown in FIG. 5 where the socket 10' is tapered, as is the shank of the fastener, which is in this instance, a sheet metal screw 26". It has been determined, for instance, for the typical installation shown being accomplished in FIG. 5, that in order to make sure that adhesive is spread high enough in the interface, that the capsule 34D should lodge in the socket 10' well-above the blind end. Accordingly, a capsule 34D has been selected which is of so great a relevant diameter, that as it is deposited in the socket 10', it only falls until it comes to rest at a similar diameter level of the socket 10' as shown. Accordingly, as the screw 26" is installed, it ruptures the capsule 34D at an earlier stage than it would have had the capsule been shorter or smaller.
The foregoing principles may be used to fasten together or consolidate any material 12 that customarily may be subjected to securement by fasteners 26, 26', 26", or by similar fasteners including jam-fit fasteners, rivets, pins and the like, made of any suitable material including but not limited to steel, aluminum, brass, wood, nylon and fiberglass reinforced plastic.
The FIG. 5 embodiment is of particular present interest because it shows one way that an adhesive containing capsule may be temporarily suspended above the bottom of the hole, or indeed without regard to whether the hole has a bottom wall or is open-ended at the bottom. However, it is required in the disclosure of this species that the socket sidewall be specially configured in relation to the adhesive-containing capsule so that the capsule becomes lodged, suspended, or the like at the desired intermediate level.
The present invention relates to means for providing the advantages of the FIG. 5 embodiment for instances where it is not feasible to directly engage the capsule of adhesive with the sidewall of the hole at an intermediate level prior to installation of the fastener. Thus the present invention is particularly useful where the hole is a straight-sided throughbore.